[ltp] One battery or two?

[Christos Papadopoulos]

Thanks for all the good info below. However, I have a few questions.

- Some people suggest unpluging the battery completely. I am a bit
  concerned about that. What if you lose power, or trip over the chord?
  Wouldn's sudden loss of power be bad for your laptop?

- About setting the charge level low (say 40%). I interpret that to mean
  that the battery will be allowed to discharge to 40% even if you are
  plugged into wall power, and then recharge. If this happens everytime,
  isn't that worse than letting your battery discharge to say 80% (for
  1 hour of battery use) and then recharge?

- If I set the recharge threshold to 40%, will my battery always discharge
  and recharge? In other words, if I am plugged in, will it still go
  through the charge cycles? If yes, how can that be good?

Christos.

On Wed, Oct 01, 2008 at 07:33:13PM -0300, Henrique de Moraes Holschuh wrote:
> On Wed, 01 Oct 2008, Tino Keitel wrote:
> > On Wed, Oct 01, 2008 at 11:02:07 -0600, Christos Papadopoulos wrote:
> > > I am facing an interesting dilemma.
> > > 
> > > I have both the regular (8-cell) and extended batteries for my X40.
> > > Which is better for maximizing battery life, leaving the extended
> > > battery plugged in, or not plugging it in?
> > 
> > In general, keeping the batteries always plugged in one of the worst
> > things you can do with your batteries. They are exposed to heat, are
> > constantly recharged and are therefore stressed a lot. You can do
> > something against the recharge cycles using tp-smapi, see below.
> 
> And if you are going to keep them unplugged, leave them at ~40% at a
> temperature in the 5°C to 15°C range, without frost.
> 
> > According to http://www.thinkwiki.org/wiki/Tp_smapi, the X40 supports
> > setting the percentage at which the battery should be recharged. If you
> > set it very low, the battery will be recharged less often.
> > 
> > I set it to 20% on my X61s. With the 8-cell battery, this gives me at
> > least one hour of remaining battery time, while keeping the number of
> > recharge cycles low.
> 
> Deep discharges are also bad.  I'd suggest never draining it below 30%
> unless you do have to (hey, not using the battery when you'd need it is a
> far worse error than using it incorrectly, as the thing will degrade with
> time anyway :-) ).
> 
> > > but "strain" the regular battery more. If I plug it in, both batteries
> > > may share the load and the recharge cycles (or does one discharge after
> > > the other?).
> 
> The batteries never share the load.  They charge and discharge one at a
> time, and the EC/BIOS is DOWNRIGHT EVIL about it at least up to the T43: it
> will fully discharge whatever battery is active before switching to the next
> one.
> 
> You *REALLY* need to use tp_smapi and some monitoring userspace thing if you
> like to use two batteries in the T4x series (and R5x) if you don't want to
> destroy your bay battery too soon (the BIOS prefers to deplete it first if
> AC goes out when both batteries are installed).  I don't know how the X40 EC
> behaves, it DOES have a slightly more advanced BIOS than the T4x, so the EC
> could be less stupid as well...
> 
> > When I used 2 batteries in my A30, they were discharged one after
> > another. With tp-smapi you should even be able to choose what battery
> > is be discharged first.
> 
> You can select which one is to be discharged, yes.  Just be careful not to
> leave the force_discharge setting enabled, because it DOES NOT GO AWAY when
> you plug in the AC adapter!
> 
> -- 
>   "One disk to rule them all, One disk to find them. One disk to bring
>   them all and in the darkness grind them. In the Land of Redmond
>   where the shadows lie." -- The Silicon Valley Tarot
>   Henrique Holschuh
> -- 
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